The present invention relates to a new and distinct cultivar of Buxus sempervirens and will be referred to hereafter by its cultivar name ‘Polar’. ‘Polar’ was discovered as a naturally-occurring whole plant variant in a cultivated area in the province of Småland in southern Sweden in 1995 by the inventor. The parentage is unknown, but is presumed to have been derived originally from a cutting of an unnamed plant of Buxus sempervirens. The climate in the province is very cold, representing zone 4 of the Swedish Hardiness Map. The age of the plant is unknown, however is thought to have existed and survived through the cold winters of the 1940s, when temperatures went below minus 40° Celsius.
‘Polar’ is a dense, medium to broad, compact woody broad-leaf evergreen that produces in an attractive ornamental plant even in colder climates, where other Boxwood cultivars produce unsatisfactory plants. The use of Boxwood in Swedish parks and gardens and other cold climates has to date been limited due to lack of hardy cultivars available on the market. The compact habit of ‘Polar’ makes it well suited for topiary as well.
The new cultivar can also be characterized by its shiny, dark green, foliage comprised of broadly elliptic leaves, with good winter color retention and resistance to winter burn.
Winter compared to the species Buxus sempervirens and the cultivars normally used in Sweden, (‘Rotundifolia’ (not patented), ‘Vrams Gunnarstorp’ (not patented), ‘Faulkner’ (not patented), ‘Arborescens’ (not patented) and ‘Blauer Heinz’ (not patented), ‘Polar’ is more dense, compact and sturdy and exhibits superior cold hardiness. ‘Polar’ can at least be grown up to zone 4 (according to the Swedish Hardiness Map), while the others can be grown only to zone 2 or zone 3. ‘Polar’ differs in plant habit in comparison to the cultivar, ‘Green Ice’. (U.S. Plant Pat. No. 10,773), in that ‘Green Ice’ is more upright in habit while ‘Polar’ develops into a plant habit where its width exceeds its height.
The leaves of ‘Polar’ are wider compared to the species Buxus sempervirens and the cultivars ‘Vrama Gunnarstorp’, ‘Faulkner’, ‘Handsworthiensis’ (not patented), and ‘Blauer Heinz’. The leaves of the cultivar ‘Rotundifolia’ are broad, but they are rounder and larger than the leaves of ‘Polar’.
Asexual reproduction of ‘Polar’ by stem cuttings was first conducted in 1995 by the inventor in Jonstorp, Sweden and propagation continued for a period of 8 years. This propagation has confirmed that the unique characteristics of ‘Polar’ are stable and are reproduced true to type in successive generations.